Various materials are used to insulate goods from shock during shipping. Solid materials such as polystyrene “peanuts,” cups and “worms,” pellets of foam rubber, plastics and expanded polyurethane foam are in common use as a shock protector. Air cushioning material, or “air pillows,” are generally preferred over the above types of dunnage because it is lighter in weight, can be supplied and dispensed in a controlled manner, and can be manufactured on site. Air Pillows are typically manufactured using rolls of sheet material, which is also easier to dispose of than the individual pieces of plastic dunnage after the product is removed.
Air pillows are typically manufactured on site because it is inefficient to ship preformed air pillows since they take up considerably more volume than the sheet material. Various devices have been described to produce sealed air dunnage, or air pillows, from sheet material. U.S. Pat. Nos. 5,188,691, 5,203,761, and 4,576,669 all propose devices for producing air filled dunnage, typically bubble wrap, from plastic sheets on an “on demand” basis.
U.S. Pat. Nos. 6,341,473, 6,889,739 and 6,948,296 each disclose a process for producing dunnage on site from plastic sheets where the plastic sheets are sealed after inflation using heating elements that contact the plastic sheets and weld them together.
However, these aforementioned processes and devices are disadvantageous in that because the heating elements must directly physically contact the plastic sheeting, they can become fouled from plastic that melts when the plastic sheeting stops moving through the devices. When heating elements become fouled, the dunnage producing machines must be cleaned or the heating elements must be replaced, resulting in down time and lost production. It is a further disadvantage that the aforementioned processes and devices are limited in their production speeds because of the need to allow the air pillow material to be physically melted between the heating elements to seal the air pillows, and because when the heating elements are fouled, speeds must be slower. Current air pillow producing machines run at speeds between 18-40 feet per minute.
Another feature of existing dunnage machines are the use of two rubber wheels that engage the plastic sheeting to pull it through the inflation and sealing process. However the use of rubber wheels is disadvantageous because when the rubber wheels get dirty, slippage in the pillow material can occur.